約束を破ったからには謝らずには済まないだろう。
- Since he broke his promise,he will have to apologize.

約束を破ったからには謝らずには済まないだろう。 meaning: Since you broke the promise, you will have to apologize.

The sentence's structure is as follows: 約束を破った (condition) からには (reason/obligation) 謝らずには済まないだろう (result/inevitability). This structure reflects a cause-and-effect relationship, emphasizing a strong consequence arising from a specific action. ⚫︎ The sentence follows a logical flow, where the first part sets up the condition, and the second part details the consequence. ⚫︎ It is a complex sentence that uses several advanced grammar points, which make it appropriate for N1 level.

からには: This is a fixed expression indicating "since," "now that," or "given that." It signifies that because a certain condition is met, a particular action or outcome is inevitable or obligatory. It implies a strong sense of responsibility or consequence. ⚫︎ Formation: (Verb/Adjective-plain form, noun + である) + からには ⚫︎ Usage: It emphasizes the speaker's recognition of the situation and the implied consequences. ⚫︎ Example: 学生であるからには、勉強をしなければならない。 - Since you are a student, you must study. ⚫︎ In this sentence, 約束を破った (past tense of "to break a promise") sets the condition. Because the promise was broken, the need to apologize is inevitable.

ずには済まない: This is a fixed expression that means "cannot help but," "must," or "cannot avoid." It expresses a strong sense of obligation or necessity, implying that something is unavoidable. The ず form is the negative stem of a verb. ⚫︎ Formation: Verb-negative stem + ずには済まない ⚫︎ Meaning: It indicates that an action or situation is unavoidable. It highlights a sense of necessity or lack of choice. ⚫︎ Example: 行かざるを得ない - Must go. 食べずには済まない - Cannot help but eat. ⚫︎ In this sentence, 謝らずには済まない indicates "cannot avoid apologizing." Because the condition is met (breaking the promise), apologizing is a must. The negative stem of 謝る is 謝ら, and adding ずには済まない results in 謝らずには済まない.

だろう: This is an auxiliary verb indicating speculation, assumption, or probability. It roughly translates to "probably," "I think," "will be," or "must be." It softens the statement, implying that the speaker is making an educated guess or inference. ⚫︎ Formation: This form follows the plain form of verbs, adjectives, and adjectival nouns. ⚫︎ Meaning: The speaker is expressing their opinion or a prediction. It does not state a definite fact, but an estimation. ⚫︎ Example: 雨が降るだろう。 - It will probably rain. ⚫︎ In this sentence, 謝らずには済まないだろう indicates the speaker's belief or expectation that the person in question *will* have to apologize, due to their action.

Verb Conjugation (Plain Forms): This sentence makes extensive use of plain forms. Understanding the plain forms of verbs is crucial for mastering complex sentence structures and fixed expressions. ⚫︎ Regular verbs have their plain form endings. For example: * 約束を破る - to break a promise (dictionary form) * 破った - broke (past plain form) * 謝る - to apologize (dictionary form) * 謝らない - not to apologize (negative plain form) ⚫︎ Irregular verbs such as する and 来る have specific plain forms to remember. ⚫︎ The ability to correctly conjugate verbs into their plain forms is fundamental for N1-level grammar.

Particles: Several particles contribute to the meaning and structure of the sentence. ⚫︎ を: The direct object marker. In this sentence, it marks the direct object of 破る ("to break"), which is 約束 ("promise"). ⚫︎ に: This particle can indicate the reason. In this sentence, it is used in the expression からには, to build up the expression of "because of." ⚫︎ These particles are essential to understand the relationships between words and phrases. A solid understanding of particles is extremely important for N1 level.